Hello and welcome to HCM, A rash with swelling on the neck is suggestive of an allergic reaction. Allergy can be due to an insect bite, spider bite, exposure to some poisonous plant or chemical in the environment, etc. Is there history of any of these complaints? If yes, then anti-histaminics are a group of drugs which are commonly used for allergic reactions. A lymph node enlargement causes a lump like swelling which is discrete and mostly mobile. A clinical examination of the rash and swelling is required for more definite opinion. Viral infections can also cause rash however, viral infections are usually associated with fever and malaise. You need to consult your doctor for clinical examination and further management. Thanks and take care Dr Shailja P Wahal